High-mobility group box 1 protein activates hepatic stellate cells in vitro.
OBJECTIVE
Our previous study noticed remarkably elevated titers of anti-high-mobility group box 1 (HMGB1) antibodies in sera during the tolerance induction phase of a rat tolerogenic orthotopic liver transplantation (OLT) as well as in sera of clinically drug-free patients. We hypothesized that the release of nonhistone nuclear protein HMGB1 during rejection may play a pathogenic role in deteriorating post-OLT graft functions, such as inducing liver fibrosis. This study sought to investigate whether HMGB1 can directly activate hepatic stellate cells (HSCs) and drive them toward fibrogenesis.


METHODS
The cultured HSCs were treated with recombinant HMGB1. RT-PCR and Western blotting analysis were used to measure alpha-smooth muscle actin (alpha-SMA) expression. Conditioned media were collected for gelatin zymography to monitor the activities of collagen-degrading matrix metalloproteinases (MMPs).


RESULTS
HMGB1 at concentrations > 1 ng/mL significantly stimulated HSC growth as revealed by proliferation and BrdU assays. alpha-SMA gene and protein expression were significantly up-regulated by HMGB1, whereas the MMP-2, but not MMP-9, activity was suppressed by HMGB1 treatment.


CONCLUSIONS
Our data suggested that HMGB1 protein, once released during the rejection phase of OLT, activated HSCs and exhibited profibrogenic effects on liver grafts either by increasing the HSC population and extracellular matrix content in liver grafts, or by transforming HSCs into myofibroblasts. Neutralization with anti-HMGB1 antibody was suggested to be a therapeutic modality applicable to prevent fibrogenesis in post-OLT liver grafts.
Kao
Y-H
YH
Department of Surgery and Liver Transplantation Program, Chang Gung Memorial Hospital - Kaohsiung Medical Center, Chang Gung University College of Medicine, Kaohsiung Hsien, Taiwan.
Jawan
B
B
Goto
S
S
Hung
C-T
CT
Lin
Y-C
YC
Nakano
T
T
Hsu
L-W
LW
Lai
C-Y
CY
Tai
M-H
MH
Chen
C-L
CL
D000199:Actins / Q000187:drug effects / Q000235:genetics*; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D005780:Gelatin / Q000378:metabolism; D024243:HMGB1 Protein / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016031:Liver Transplantation / Q000473:pathology / Q000502:physiology; D020778:Matrix Metalloproteinase 2 / Q000187:drug effects / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000199:Actins; D005780:Gelatin; D024243:HMGB1 Protein; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; C498862:Acta2 protein, rat